1. Field of the Invention
The invention relates generally to active solar hot water systems employing a drainback tank for storing the thermally conductive recirculation fluid during periods of system shutdown.
2. Description of the Prior Art
Most active solar systems employ two liquid systems, a hot water utilization system including a potable hot water storage tank having cold water inlet and hot water outlet lines, and a recirculating, solar heated fluid system including a solar collection panel, a "drainback" tank, and a heat exchange coil. In some active systems, these individual components have been combined or integrated, in various ways, usually to increase freeze protection or to simplify the system's overall complexity.
U.S. Pat. No. 4,257,479, issued to Newton, discloses a combined heat exchanger and draindown tank for an active solar system.
In Collins, U.S. Pat. No. 4,285,334, the potable hot water storage tank includes an internal heat exchanger unit for receiving liquid heated in the solar collection panel and for storing same during system shutdown.
U.S. Pat. No. 4,326,499, issued to Koskelo, illustrates a combined heat exchanger and draindown tank, actively interconnected to the solar circulating system and designed for heating water in the storage tank by means of thermal siphoning.
Muller, U.S. Pat. No. 4,253,446 teaches a water storage reservoir partitioned into hydraulically interconnected upper and lower tanks.
None of this art, however, suggests a purely active solar hot water system in which the solar collection unit, the heat exchanger unit, and the drain down tank are ordered respectively in vertically descending relation, in the manner set forth herein.